The present invention relates to a protractor for measuring a voluntary angle and, more particularly, an electronic combined protractor and calculator which can be used for measuring a voluntary angle and length of an object with a tape member extensible out of the housing thereof.
A prior art protractor was disclosed in U.S. Pat. No. 3,996,670 "PROTRACTOR WITH DIGITAL READOUT" issued on Dec. 14, 1976. The protractor was a type of a propeller protractor for measuring a blade angle of blades. In other words, a voluntary angle except for the blade angle could not be measured using the above protractor. A protractor which can measure any angle of an object is most preferable.